1. Field of the Invention
The present invention relates to a clamp apparatus, which is capable of clamping a workpiece via a rotatable clamp arm that is rotated through a predetermined angle under a displacement operation of a piston.
2. Description of the Related Art
Heretofore, for example, when constituent parts of an automobile or the like are welded, a clamp apparatus has been used for clamping the parts.
The clamp apparatus, for example as disclosed in U.S. Pat. No. 5,503,378, comprises a main body equipped with a piston that is displaced under the supply of a pressure fluid, a pair of clamp arms which are retained rotatably with respect to the main body, and a toggle link mechanism through which a driving force from the main body is transmitted to the clamp arm. In addition, rotating rollers that make up part of the toggle mechanism are inserted into guide grooves formed respectively on both side surfaces of the main body. Moreover, the rollers are inserted through groove portions of the clamp arms, and the rollers are displaced along an axial direction upon displacement of the piston. As a result, the clamp arms are rotated by a predetermined angle about a support, and corresponding to the direction of rotation, a clamped state capable of clamping the workpiece, and an unclamped state in which the clamped condition is released, are switched.
However, with such a conventional technique, because a structure is provided made up from the pair of clamp arms, two rotating rollers are required along therewith, which engage with the clamp arms, and additionally, a pair of guide grooves in the main body through which the rollers are inserted, respectively, also are required. Further, because the guide grooves in which the rollers are guided are disposed directly in both side surfaces of the main body, a cover plate also is needed for the purpose of closing the guide grooves. As a result, the number of parts needed to construct the clamp apparatus increases, and the structure thereof is complex, which decreases the ease of assembly thereof when the clamp apparatus is manufactured.